Spark plug



J. BLACKBURN SPARK PLUG Filed Dec. 27, 1920 Patented Aug. 5, 1924.

JASIYE'EB, BLACKBURN, OF ST. LOUIS, MISSOURI.

'SPARK PLUG.

Application led December 27, 1920.

T 0 all whom t may concern.'

Be it known that I, JAsPEr. BLACKBURN, a citizen of the United States, and resident of the city of St. Louis, State of Missouri, have invented certain new and useful Improvements in Spark Plugs, of which the following is a specification, containing a full, clear, and exact description, reference being had to the accompanying drawings, forming a part hereof.

My invention relates to improvements in spark plugs, and has for its principal oblject the construction of a plug wherein the spark gapis easily adjusted and maintained.

In the drawings- Fig. 1 is a longitudinal section of my spark plug; and

Fig. 2 is a transverse section taken through the insulator, the electrodes and the spark ap. g Referring by numerals to the accompanying drawings- 3 indicates a casing provided on its lower end with the usual screw threads 4, by means of which the plug may be attached to an engine, and it' is also provided. with. a central bore and internal screwthreads 5 and with ashoulder 6, the latter being provided as a support for the insulator.

7 indicates a jamb nut for holding the parts of the plug in position. 8 indicates the. insulator, which is formed integral and is provided in its lower portion with a. cen tral bore 9 in whichthere is mounted an electrode 10, and it is also provided in its upper portion with a larger and concentric bore 11 in which is mounted a tubular elec trode 12 whose internal diameteris larger than the diameter of the electrode 10.

The electrode 12 is slightly shorter than the depth of 'the bore in which it` is located. 13 indicates a. cap having a flange 14 capable of being crimped into the groove 15 by means of which the cap is securely united to the upper end of the insulator 8.

The upper surface of the cap 13 is provided with a screw-threaded stem adapted to receive the binding nut 16 and is further provided on its lower surface with a projection or stem 17 adapted to snugly t in the upper end of the hollow electrode 12.

Formed in the insulator 8 on which the tubular electrode is seated, is a shoulder 18.

Serial No. 433,161.

The hollow electrode 12 is preferably provided with indentations 19 from which the spark emanates or passes to the electrode 10.

In assembling, the lower electrode 10 is inserted in its appropriate bore, the upper end projecting above the shoulder 18 and upwardly and within the tubular electrode 12. The electrodes 10 and 12 are cemented and baked in the usual manner.

From the foregoing construction, it will be seen that the spark passes from the inner surface of the tubular electrode 12 to the electrode 10 and the spark gap is determined from the internal diameter of )the hollow electrode 12 and the diameter of the lower electrode 10 and, as stated more accurately, between the inner surfaces of the dents 19 and the exterior surface of the electrode 10.

From the foregoing it is obvious that no delicate adjustment is required to make the spark gap and after being made, it is impossible for the parts to get out of adjustment, for the reason that the electrode 10 is inserted far enough into the hollow electrode 12 so as to provide for any slight displacement of the electrode..

Having fully described my invention, what I claim is:

In a. spark plug, a casing having a one piece insulator secured therein, said insulator being provided with an upper and a lower concentric bore., the lower bore being of less diameter than the upper bore so as to form a shoulder approximately midway the length of the insulator, a tubular upper electrode secured in the upper bore and of approximately the same length as said bore and having indentations formed adjacent its lower end, a lower electrode secured in the lower bore, said electrode. extending beyond the lower end of the insulator and into the tubular electrode and spaced apart there; from so as to form a spark gap, a metallic cap secured to the upper end of the insulator, said cap being provided with. a central projection adapted to tit snugly within the tubular electrode so as to forni an electrical connection therewith, and means for securing an electric conductor to said cap.

In testimony whereof, I have signed my name to this specification.

JASPER BLACKBURN. 

